Azeotropic or pseudo-azeotropic composition and use of these compositions

ABSTRACT

1,1,1,3,3-Pentafluorobutane forms azeotropic or pseudoazeotropic compositions with alkanes possessing 5 or 6 carbon atoms. These compositions can be used in particular as blowing agents in polymeric cellular foams.

The invention relates to compositions comprising1,1,1,3,3-pentafluorobutane (also known as HFC-365mfc) and to the use ofthese compositions, in particular as blowing agents for polymericcellular foams and more particularly for polyurethane foams.

It is well known that polyurethane foams can be prepared by reacting anisocyanate with an appropriate amount of a polyol or of a mixture ofpolyols in the presence of a blowing agent consisting of a volatileliquid, which is evaporated by the heat given off by the reactionbetween the isocyanate and the polyol. Trichlorofluoromethane (CFC-11),dichlorodifluoromethane (CFC-12) and, to a lesser extent,chlorodifluoromethane (HCFC-22), 1,1,2-trichlorotrifluoroethane(CFC-113) and 1,2-dichlorotetrafluoroethane (CFC-114) have been used fora long time as blowing agents. Because of its very low thermalconductivity, CFC-11 makes it possible to obtain particularly insulatingrigid polyurethane foams, which are intensively used as thermalinsulators, in particular in the fields of construction, refrigerationand transportation.

However, fully halogenated chlorofluorinated hydrocarbons (CFCs) aresuspected of causing environmental problems, mainly in the context ofthe destruction of the stratospheric ozone layer. They are today bannedin the majority of their conventional applications.

Chlorine-free hydrofluoroalkanes are completely inert with respect tothe stratospheric ozone layer and these compounds are findingincreasingly wide use in numerous applications, to the detriment ofcompounds carrying chlorine atoms. Thus, 1,1,1,3,3-pentafluorobutane(HFC-365mfc) has been proposed in various applications. Japanese PatentApplications JP 05/168805 and JP 05/171190 describe solvent compositionscomprising 1,1,1,3,3-pentafluorobutane, a cosolvent soluble in1,1,1,3,3-pentafluorobutane and optionally a surfactant. Thesecompositions can be used in operations for cleaning objects or for theremoval of residual water in the electronics industry. The only binarycompositions described comprise 4% of n-pentane, 10% of cyclopentane oralternatively 5% of hexane.

Murphy and his coworkers (International CFC and Halon AlternativesConference, Washington D.C., 1993, pp. 346-355) have described the useof cyclopentane/HFC-365mfc binary mixtures containing at least 54% byweight of cyclopentane as blowing agent for polyurethane foams. However,it has been noticed that there is a risk, in certain cases and undercertain circumstances, of HFC-365mfc and the mixtures mentioned abovecondensing in the cells of the foam, resulting, if the case arises, in adeterioration in its thermal conductivity and optionally in itsmechanical properties.

The need thus remains to find blowing agent compositions for polymericcellular foams which are devoid of harmful effect on the environment,which have a boiling point close to the boiling point of CFC-11 or1,1-dichloro-1-fluoroethane (HCFC-141b) and which possess the physicalproperties which make it possible to form polymeric cellular foams oflow thermal conductivity in a wide range of temperatures, particularlyfoams with closed cells of homogeneous size.

One of the objects of the present invention is to provide compositionswhich perform particularly well when they are used as blowing agents, inparticular for the manufacture of polyurethane foams. Another object ofthe invention is to provide such compositions which are devoid ofdestructive effect with respect to the ozone layer and which canconsequently be used as replacement for compositions based on fullyhalogenated chlorofluoroalkanes, such as CFC-11, or on partiallyhalogenated hydrocarbons containing chlorine atoms, such as HCFC-141b.

The present invention consequently relates to compositions composedessentially of 1,1,1,3,3-pentafluorobutane and of an alkane possessing 5or 6 carbon atoms, which are characterized in that they are azeotropicor pseudoazeotropic.

The thermodynamic state of a fluid is fundamentally defined by fourinterdependent variables: the pressure (P), the temperature (T), thecomposition of the liquid phase (X) and the composition of the gas phase(Y). A true azeotrope is a specific system containing 2 or morecomponents for which, at a given temperature and at a given pressure,the composition of the liquid phase X is exactly the same as thecomposition of the gas phase Y. A pseudoazeotrope is a system containing2 or more components for which, at a given temperature and at a givenpressure, X is substantially the same as Y. In practice, this means thatthe constituents of such azeotropic and pseudoazeotropic systems cannotbe easily separated by distillation and, consequently, their compositionremains constant in polymeric cellular foam blowing operations.

For the purposes of the present invention, pseudoazeotropic mixture isunderstood to mean a mixture of two constituents, the boiling of which(at a given pressure) differs from the boiling point of the trueazeotrope by at most 0.5° C. Mixtures for which the boiling pointdiffers from the boiling point of the true azeotrope by at most 0.2° C.are preferred. Mixtures for which the boiling point differs from theboiling point of the true azeotrope by at most 0.1° C. are particularlypreferred.

The alkanes possessing 5 or 6 carbon atoms which can be used in thecompositions according to the invention can be linear, branched orcyclic. Among all the possible isomers of the hydrocarbons possessing 5or 6 carbon atoms, linear pentane (or n-pentane), isopentane (or2-methylbutane), cyclopentane and linear hexane (or n-hexane) arepreferred. The latter form, with 1,1,1,3,3-pentafluorobutane, azeotropicor pseudoazeotropic compositions with a minimum boiling point.

The azeotropic and pseudoazeotropic binary mixtures formed between1,1,1,3,3-pentafluorobutane and cyclopentane are particularly preferred.

The relative contents of 1,1,1,3,3-pentafluorobutane and of alkanepossessing 5 or 6 carbon atoms in the compositions according to theinvention can vary within wide proportions, provided that thecompositions thus formed are azeotropic or pseudoazeotropic with aminimum boiling point.

The compositions of the azeotropic mixtures according to the inventionwere estimated by calculation on the basis of the results of theexperimental measurements presented in the examples below.

1,1,1,3,3-Pentafluorobutane and n-pentane form a binary azeotrope orpseudoazeotrope when their mixture contains approximately from 24 to 60%by weight of n-pentane. The binary compositions containing approximatelyfrom 30 to 53% by weight of n-pentane are preferred. The binarycompositions containing approximately from 32 to 47% by weight areparticularly preferred. Under a pressure of 103.5 kPa, the binarycomposition composed essentially of approximately 66% by weight of1,1,1,3,3-pentafluorobutane and of approximately 34% by weight ofn-pentane constitutes a true azeotrope, the boiling point of which isapproximately 27.4° C. This composition is very particularly preferred.1,1,1,3,3-Pentafluorobutane and cyclopentane form a binary azeotrope orpseudoazeotrope when their mixture contains approximately from 16 to 46%by weight of cyclopentane. The binary compositions containingapproximately from 18.5 to 39% by weight of cyclopentane are preferred.The binary compositions containing approximately from 20 to 35% byweight of cyclopentane are particularly preferred.

Under a pressure of 101.4 kPa, the binary composition composedessentially of approximately 78.5% by weight of1,1,1,3,3-pentafluorobutane and of approximately 21.5% by weight ofcyclopentane constitutes a true azeotrope, the boiling point of which isapproximately 32.2° C. This composition is very particularly preferred.

1,1,1,3,3-Pentafluorobutane and isopentane form a binary azeotrope orpseudoazeotrope when their mixture contains approximately from 31 to 75%by weight of isopentane. The binary compositions containingapproximately from 39 to 70% by weight of isopentane are preferred. Thebinary compositions containing approximately from 45 to 60% by weight ofisopentane are particularly preferred. Under a pressure of 101.2 kPa,the binary composition composed essentially of approximately 53% byweight of 1,1,1,3,3-pentafluorobutane and of approximately 47% by weightof isopentane constitutes a true azeotrope, the boiling point of whichis approximately 22.5° C. This composition is very particularlypreferred.

1,1,1,3,3-Pentafluorobutane and n-hexane form a binary azeotrope orpseudoazeotrope when their mixture contains approximately from 6 to 29%by weight of n-hexane. The binary compositions containing approximatelyfrom 9.5 to 24% by weight of n-hexane are preferred. Under a pressure of102.1 kPa, the binary composition composed essentially of approximately90% by weight of 1,1,1,3,3-pentafluorobutane and of approximately 10% byweight of n-hexane constitutes a true azeotrope, the boiling point ofwhich is approximately 37.9° C. This composition is very particularlypreferred.

The invention also relates to the use of the compositions according tothe invention for the blowing of polymeric cellular foams.

The polymeric cellular foams can be obtained according to variousprocesses. A commonly used process consists in injecting, underpressure, a blowing agent into a molten polymeric mixture to be expandedin an extruder. The decompression obtained at the outlet of the extruderresults in the expansion of the polymeric mixture with formation of afoam composed of cells filled with the blowing agent. Polystyrene foamsare generally obtained by this process. Another process, typically usedto manufacture polyurethane or polyisocyanurate foams, consists inreacting an isocyanate with an appropriate amount of a polyol or of amixture of polyols, in the presence of a blowing agent consisting of avolatile liquid, which is evaporated by the heat given off by thereaction between the isocyanate and the polyol. The compositionsaccording to the invention are particularly recommended for the blowingof polyurethane or polyisocyanurate foams, very particularly formanufacturing rigid foams. In this case, use is generally made of 1 to40, typically of 15 to 35, parts by weight of blowing agent per 100parts by weight of polyol.

The invention also relates to blowing agents for polymeric cellularfoams, which are characterized in that they contain an azeotropic orpseudoazeotropic composition according to the invention.

The blowing agents containing a composition according to the inventioncomposed of 1,1,1,3,3-pentafluorobutane and of cyclopentane areparticularly suited to the preparation of polyurethane orpolyisocyanurate foams.

In an alternative form in accordance with the invention, the blowingagents also contain n-butane or isobutane, typically from 2 to 20% byweight, preferably from 5 to 15% by weight.

The blowing agents for polymeric cellular foams can also contain astabilizer of the azeotropic or pseudoazeotropic composition accordingto the invention, such as nitromethane or a-methylstyrene.

The azeotropic or pseudoazeotropic compositions according to theinvention can be used in premixes for polyurethane or polyisocyanuratefoams. Such premixes contain at least one polyol, one azeotropic orpseudoazeotropic composition according to the invention and optionallyvarious additives commonly used for preparing polyurethane orpolyisocyanurate foams, such as, in particular, water, catalysts,surface-active agents, antioxidizing agents, flame-retardant agentsand/or pigments. The premixes containing the azeotropic orpseudoazeotropic compositions according to the invention also form partof the present invention.

The invention also relates to the use of the azeotropic orpseudoazeotropic compositions described above as refrigerating fluids,as solvents, as desiccating agents or as degreasing agents for solidsurfaces.

The non-limiting examples hereinbelow illustrate the invention in a moredetailed way.

EXAMPLES 1-4

In order to demonstrate the existence of azeotropic or pseudoazeotropiccompositions according to the invention between1,1,1,3,3-pentafluorobutane and a hydrocarbon possessing 5 or 6 carbonatoms, a glass device composed of a 50 ml distillation flask surmountedby a reflux condenser was used. The temperature of the liquid wasmeasured by means of a thermometer immersed in the flask.

An amount of pure 1,1,1,3,3-pentafluorobutane determined with accuracywas heated under a known pressure to boiling point and then smallamounts of hydrocarbon, weighed with accuracy, were gradually introducedinto the flask, by means of a syringe, via a side arm.

The pseudoazeotropic compositions were determined by plotting the changein the boiling temperature of the mixture as a function of itscomposition.

These measurements were made for mixtures containing1,1,1,3,3-penta-fluorobutane and increasing amounts of n-pentane(Example 1), of cyclopentane (Example 2), of isopentane (Example 3) orof n-hexane (Example 4).

The pressure at which the measurements were taken is mentioned. Thechange in the boiling temperature of the various compositions as afunction of their hydrocarbon content, expressed as weight %, ispresented in Table I.

TABLE I Example 2 Example 3 Example 1 HFC-365 mfc/ HFC-365 mfc/ Example4 HFC-365 mfc/ cyclopentane isopentane HFC-365 mfc/ n-pentane (Pressure:(Pressure: n-hexane (Pressure: 101.4 kPa) 101.2 kPa) (Pressure: 103.5kPa) Cyclo- Isopent- 102.1 kPa) Pentane B.t. pentane B.t. ane B.t.Hexane B.t. (wt. %) (° C.) (wt. %) (° C.) (wt. %) (° C.) (wt. %) (° C.)0 40.6 0 40.3 0 40.3 0 40.5 1.32 39.2 2.96 37.6 1.14 38.9 1.36 39.9 2.5237.5 4.88 36.0 4.43 34.5 2.58 39.4 3.63 36.0 7.09 34.8 5.96 32.3 3.1439.2 4.39 35.1 8.75 34.1 7.5 30.6 4.19 38.9 5.2 34.1 10.64 33.6 8.9329.2 5.71 38.6 6.49 32.7 12.4 33.2 12.7 27.0 7.79 38.3 9.2 31.0 14.2232.8 14.94 26.2 9.76 38.1 11.01 30.2 16.04 32.6 18.48 24.6 11.14 38.012.26 29.7 17.7 32.5 20.96 24.2 13.15 37.9 15.51 28.8 19.2 32.3 25.8623.6 15 37.9 16.93 28.6 21.36 32.2 29.25 23.2 16.7 37.9 18.87 28.3 23.2932.2 32.64 22.9 18.31 38.0 20.77 28.1 25.19 32.2 37.09 22.8 20.13 38.022.53 28.0 27.57 32.2 41.19 22.6 21.74 38.0 24.3 27.9 30.35 32.2 45.0622.6 23.36 38.1 26.68 27.8 31.45 32.2 48.41 22.5 25.26 38.2 29.35 27.633.74 32.2 51.07 22.5 28.78 38.4 31.9 27.5 36.28 32.3 54.35 22.5 33.1638.6 34.6 27.4 38.95 32.4 56.69 22.5 36.6 38.7 37.11 27.4 41.99 32.558.93 22.5 40.34 39.0 39.46 27.4 46.41 32.6 60.65 22.5 43.54 39.4 41.627.4 53.88 33.0 70.14 22.7 49.35 39.8 44.02 27.4 57.97 33.3 74.77 23.056.48 41.0 53 27.6 66.68 33.9 80.28 23.6 56.69 41.6 59.56 27.8 71.7634.7 89.84 25.1 67.28 43.4 65.96 28.2 79.47 36.7 100 28.0 77.13 47.271.65 28.8 92.94 43.3 88.13 54.3 100 36.6 100 49.3 100 67.0

EXAMPLES 5-8

Polyurethane foams were prepared starting from the same formulation butusing, as blowing agent, either HFC-365mfc (Example 5), cyclopentane(Example 6), an HFC-365mfc/cyclopentane composition composed, by weight,of 72 parts of HFC-365mfc and of 28 parts of cyclopentane (Example 7)and an HFC-365mfc/n-pentane composition composed, by weight, of 58.4parts of HFC-365mfc and of 41.6 parts of n-pentane (Example 8). Thethermal conductivity (Lambda) of these foams was subsequently measuredat different temperatures. The variations in thermal conductivity arepresented in Table II. The thermal conductivity, measured at 24° C., ofa foam obtained with HFC-365mfc was taken as reference. The variationsare expressed as percents with respect to this reference. A positivevariation corresponds to an increase in conductivity, that is to say toa decrease in the insulating power of the foam.

TABLE II Example 5 Example 6 Example 7 Example 8 Blowing HFC-365- Cyclo-HFC-365 mfc/ HFC-365 mfc/ agent mfc pentane cyclopentane n-pentaneVariation in conductivity (%) at −7.5° C. +6.4 +2.4 0 +2.8 at 0° C. +4.8+2 −1.6 +1.2 at 10° C. +1.2 +1.2 −6 +1.2 at 24° C. 0 +2.4 0 +2.4

Whereas the thermal conductivity in the gas phase of cyclopentane ishigher than that of HFC-365mfc (respectively 12 and 10.6 mW/m.K at 25°C.), a polyurethane foam blown with the1,1,1,3,3-pentafluorobutane/cyclopentane azeotropic mixture exhibits, atlow temperature, a lower thermal conductivity than that of a comparablefoam blown with HFC-365mfc, in the absence of cyclopentane.

Similar results are obtained with the HFC-365mfc/n-pentane azeotropiccomposition.

What is claimed is:
 1. In a method for manufacturing a polymericcellular foam, the improvement which consists in selecting a blowingagent comprising a composition forming a minimum boiling point binaryazeotrope or pseudo-azeotrope at atmospheric pressure, said compositionbeing selected from (a) a composition consisting of from approximately47 wt % to 70 wt % of 1,1,1,3,3-pentafluorobutane and from approximately30 wt % to 53 wt % of n-pentane; (b) a composition consisting of fromapproximately 61 wt % to 81.5 wt % of 1,1,1,3,3-pentafluorobutane andfrom 18.5 wt % to 39 wt % of cyclopentane; (c) a composition consistingof form approximately 30 wt % to 61 wt % of 1,1,1,3,3-pentafluorobutaneand from approximately 39 wt % to 70 wt % of isopentane; and (d) acomposition consisting of from approximately 76 wt % to 91.5 wt % of1,1,1,3,3-pentafluorobutane and from approximately 9.5 wt % to 24 wt %of n-hexane.
 2. A polymeric cellular foam which is obtained by theprocess as claimed in claim
 1. 3. The polymeric cellular foam as claimedin claim 2, wherein the foam is polyurethane or polyisocyanurate.
 4. Theprocess as claimed in claim 1, wherein the blowing agent is present in 1to 40 parts by weight per 100 parts by weight of said polyol.
 5. Theprocess as claimed in claim 4, wherein the blowing agent is in amount of15 to 35 parts by weight per 100 parts by weight of said polyol.
 6. Theprocess as claimed in claim 5, wherein the foam is a polyurethane foam.7. The process as claimed in claim 1, wherein the composition containsapproximately 66% by weight of 1,1,1,3,3-pentafluorobutane andapproximately 34% by weight of n-pentane, and the composition has aboiling point of approximately 27.4° C. under a pressure of 103.5 kPa.8. The process according to claim 1, wherein the composition contains aapproximately 78.5% by weight of 1,1,1,3,3-pentafluorobutane andapproximately 21.5% by weight of cyclopentane and the composition has aboiling point of approximately 32.2° C. under a pressure of 101.4 kPa.9. The process according to claim 1, wherein the composition containsapproximately 53% by weight of 1,1,1,3,3-pentafluorobutane andapproximately 47% by weight of isopentane and the composition has aboiling point of approximately 22.5° C. under a pressure of 101.2 kPa.10. The process according to claim 1, wherein the composition containsapproximately 90% by weight of 1,1,1,3,3-pentafluorobutane andapproximately 10% by weight of n-hexane and the composition has aboiling point of approximately 37.9° C. under a pressure of 102.1 kPa.11. A method for manufacturing a polymeric cellular foam, whichcomprises reacting an isocyanurate with a polyol or mixture of polyolsin the presence of a blowing agent and said blowing agent comprises acomposition forming a minimum boiling point binary azeotrope orpseudo-azeotrope at atmospheric pressure, said composition beingselected from (a) a composition consisting of from approximately 47 wt %to 70 wt % of 1,1,1,3,3-pentafluorobutane and from approximately 30 wt %to 53 wt % of n-pentane; (b) a composition consisting of fromapproximately 61 wt % to 81.5 wt % of 1,1,1,3,3-pentafluorobutane andfrom 18.5 wt % to 39 wt % of cyclopentane; (c) a composition consistingof form approximately 30 wt % to 61 wt % of 1,1,1,3,3-pentafluorobutaneand from approximately 39 wt % to 70 wt % of isopentane; and (d) acomposition consisting of from approximately 76 wt % to 91.5 wt % of1,1,1,3,3-pentafluorobutane and from approximately 9.5 wt % to 24 wt %of n-hexane.
 12. An azeotrope composition consisting essentially of (a)a composition consisting of from approximately 47 wt % to 70 wt % of1,1,1,3,3-pentafluorobutane and from approximately 30 wt % to 53 wt % ofn-pentane; (b) a composition consisting of from approximately 61 wt % to81.5 wt % of 1,1,1,3,3-pentafluorobutane and from 18.5 wt % to 39 wt %of cyclopentane; (c) a composition consisting of form approximately 30wt % to 61 wt % of 1,1,1,3,3-pentafluorobutane and from approximately 39wt % to 70 wt % of isopentane; or (d) a composition consisting of fromapproximately 76 wt % to 91.5 wt % of 1,1,1,3,3-pentafluorobutane andfrom approximately 9.5 wt % to 24 wt % of n-hexane.
 13. An azeotropecomposition according to claim 12, wherein the composition containsapproximately 66% by weight of 1,1,1,3,3-pentafluorobutane andapproximately 34% by weight of n-pentane, and the composition has aboiling point of approximately 27.4° C. under a pressure of 103.5 kPa.14. The azeotrope composition according to claim 12, wherein thecomposition contains a approximately 78.5% by weight of1,1,1,3,3-pentafluorobutane and approximately 21.5% by weight ofcyclopentane and the composition has a boiling point of approximately32.2° C. under a pressure of 101.4 kPa.
 15. The azeotrope compositionaccording to claim 12, wherein the composition contains approximately53% by weight of 1,1,1,3,3-pentafluorobutane and approximately 47% byweight of isopentane and the composition has a boiling point ofapproximately 22.5° C. under a pressure of 101.2 kPa.
 16. The azeotropecomposition according to claim 12, wherein the composition containsapproximately 90% by weight of 1,1,1,3,3-pentafluorobutane andapproximately 10% by weight of n-hexane and the composition has aboiling point of approximately 37.9° C. under a pressure of 102.1 kPa.